You are correct:
My camera is pink, and my mobile phone is black.
These are two independent clauses, joined by a comma and the word and. This is the textbook example of how to correctly join two independent clauses with a coordinating conjunction.
My camera is small. my phone is small, too.
This is incorrect. You finished the first sentence (because it ended with a period) but then started the second sentence with a lowercase letter. If you want to join these two sentences (independent clauses) into a single sentence without using a coordinating conjunction (e.g. and), you can use a semicolon:
My camera is small; my phone is small, too.
My camera is pink; my mobile phone is black.
For comma usage rules, I would start with a search engine and the web. Here's a place to start: http://www.grammarbook.com/punctuation/commas.asp
For long term learning and use, I would pick up a proper writer's guide, such as The Holt Handbook, The Chicago Manual or Style, or The Writer's Reference. (These aren't endorsements of these specific books, but rather examples of what I mean when I say a writer's guide.)